1. Field of the Invention
The present invention relates generally to the field of valves, and more particularly, to a stemless ball valve.
2. Description of the Related Art
Valves have been used for centuries in many different ways to control fluids. Fluid technology has progressed, especially since the Industrial Revolution. As a result, a great variety of uses have been found for valves. Some of these uses include pneumatic and motor-driven actuation with controllers that are regulated by a computer. By and large, however, the basic flow design of valves has stayed relatively constant along four basic lines.
The first of these is the gate valve. It is simple in design, inexpensive to make, and can be used in a variety of applications. A gate valve typically contains a circular disk known as the gate. It is mounted perpendicular to the pipe containing the fluid. Reciprocal actuation guides the gate up and down into the seat of the valve to either open the flow path for full flow or to close it down. Because of inherent deficiencies in design, gate valves are rarely used to modulate the rate of flow of fluid through the valve.
A second typical style of valve is the globe valve. These valves are very good at throttling, but with reduced flow capabilities. The path of the fluid through the valve is tortuous, and as a result, these valves do not allow as much fluid flow for a given size as the other basic valve designs.
A third (and the most popular) design is the ball valve. The valve actuator is connected by a valve stem to a ball inside the valve. The ball has a large hole bored inside of it from one side to the other. Rotating the ball allows for this hole to be aligned with the incoming and outgoing flow path. In the closed position, the ball opening is rotated perpendicular to the flow path and completely shuts off the flow of fluid. “Full port” ball valves have a hole that is the same diameter as the incoming and outgoing pipelines. This is the most efficient of all valves—the one that offers the least resistance to the flow of the fluid in the fully open position.
A fourth basic type of valve is known as the butterfly valve. The butterfly valve has an internal seat that is perpendicular to the flow of the fluid. The valve stem connects to and rotates a circular disk inside the valve to engage the seat to block fluid flow. A butterfly valve generally has high flow rates like the ball valve, but unlike the ball valve, the circular disk stays in the fluid path and can catch debris that might be present in the fluid.
All of the above-mentioned valve types require stems. The stem is the component that transfers mechanical action from outside of the valve to the inside, effecting a change in the flow of the fluid through the valve. All valve stems penetrate the body of valves, and this necessitates a sealing device or packing around the stem to prevent the internal fluid of the valve from leaking to the outside through the stem hole. There is a constant quest for better sealing methods around valve stems, especially today when the leakage of hazardous fluids can damage the environment or injure people in the vicinity of the valve. Valve stem leakage is also the major cause of air pollution or fugitive emission discharges from refiners and chemical process systems. There are even secondary containment systems developed to contain potential leakage from valve stems. For example, bellows are used on reciprocally actuated valve stems (gate and globe types) to encase the stem and the packing within it. The pleats of the bellows expand and contract just like the pleats on an accordion to accommodate the motion of the valve stem. Unfortunately, bellows and other types of containment can fail, resulting in a catastrophic release of fluid entrapped between the valve stem and the containment unit.
With the advent of modern powerful magnetic materials, it is now possible to actuate the internals of a valve without the use of a valve stem. By using magnetic fields to transfer mechanical power to the internal mechanism of a valve, it is no longer necessary to penetrate the body of the valve with a stem hole.
The valve described in U.S. Pat. No. 6,109,293 (Walrath et at, 2000) represents a significant improvement over stemmed valves. This patent utilizes modern permanent magnets to transfer the necessary torque to the valve internals without the use of a valve stem. Internally the valve stem consists of an offset venturi that has been split at the most restrictive point in the venture passage. By rotating one side or the other, this configuration becomes a valve capable of controlling fluid flow. The mechanical energy applied to the outside array of permanent magnets is transferred to an internal array of magnets that initiate the rotational movement required by the valve.
Other variations of this design employ a rotating disk or wafer, but the basic principal of operation remains the same, relying on magnetic fields rather than a valve stem to actuate the valve. Unfortunately, the seal designs employed in these embodiments are prone to failure under high flow conditions and simply cannot compete with the standard seal designs employed by the other valve types.
Accordingly, it is an object of the present invention to incorporate accepted and proven ball valve sealing technology into a stemless valve design that can be used to control fluids. Between fifty and seventy percent of all valve maintenance is associated with packing or mechanical seal failure on valve stems; therefore, it is a further object to provide a valve that avoids this maintenance by eliminating the valve stem entirely while still providing a high level of fluid control.